//constant:
// Integer
// Float
// String
// Boolean
//symbol:
// ReplacementSymbol
// Symbol
//value:
// constant
// symbol
// operation
// scope
//operation: value Operator value
//list-expression: value-source , value-source
//scope: StartScope value-source EndScope
//value-source:
// value
// scope
// function
// operation
//function: symbol StartScope list-expression EndScope | symbol StartScope value-source EndScope
public static Expression Parse(List <Token> tokens)
{
if (tokens == null || tokens.None())
{
return(new NullExpression());
}
var remainder = tokens.ToList();
Expression program = null;
while (remainder.Any())
{
Production parsed = null;
var current = remainder.First();
switch (current.TokenClass)
{
case TokenClass.StartScope:
parsed = new ScopedExpression().Parse(remainder);
if (parsed.Expression != null)
{
break;
}
parsed = new SeparatedExpression().Parse(remainder);
if (parsed.Expression != null)
{
break;
}
parsed = new ErrorExpression().Parse(program, remainder);
break;
case TokenClass.Whitespace:
parsed = new WhitespaceExpression().Parse(remainder);
break;
case TokenClass.Symbol:
parsed = new OperationExpression().Parse(remainder);
if (parsed.Expression != null)
{
break;
}
parsed = new FunctionExpression().Parse(remainder);
if (parsed.Expression != null)
{
break;
}
parsed = new SymbolExpression().Parse(remainder);
if (parsed.Expression != null)
{
break;
}
parsed = new ErrorExpression().Parse(program, remainder);
break;
case TokenClass.ReplacementSymbol:
parsed = new OperationExpression().Parse(remainder);
if (parsed.Expression != null)
{
break;
}
parsed = new ReplacementSymbolExpression().Parse(remainder);
break;
case TokenClass.Float:
case TokenClass.Integer:
parsed = new OperationExpression().Parse(remainder);
if (parsed.Expression != null)
{
break;
}
parsed = NumericExpression.TryParseNumeric(remainder);
break;
case TokenClass.String:
parsed = new OperationExpression().Parse(remainder);
if (parsed.Expression != null)
{
break;
}
parsed = new StringExpression().Parse(remainder);
break;
case TokenClass.Boolean:
parsed = new OperationExpression().Parse(remainder);
if (parsed.Expression != null)
{
break;
}
parsed = new BooleanExpression().Parse(remainder);
break;
case TokenClass.Operator:
parsed = NumericExpression.TryParseNumeric(remainder);
if (parsed.Expression != null)
{
break;
}
parsed = new OperationExpression().Parse(program, remainder);
if (parsed.Expression != null)
{
break;
}
parsed = new ErrorExpression().Parse(program, remainder);
break;
case TokenClass.Error:
throw new Exception("Unexpected sequence: " + remainder.First().Lexeme);
default:
throw new ArgumentOutOfRangeException();
}
if (parsed.Expression != null && !(parsed.Expression is WhitespaceExpression))
{
program = parsed.Expression;
}
remainder = parsed.RemainingTokens;
}
if (program == null || remainder.Any())
{
throw new ParserException(remainder.Select(c => c.Lexeme).StringConcat());
}
return(program);
}
protected override Expression Visit(ScopedExpression node) => node.Expression;
